Hydraulic pump



Dec. 26, 1967 D.YC.HALSEY HYDRAULIC PUMP Filed oct." 22, 1965 5 sheets-sheet 1 INVENTOR. ,Zan/ Half@ y* .I' Alg if l l Ill l /7 7 far/Vg@ Dec. 26,1967

Filed Oct. 22, 1965 D. C. HALSEY HYDRAULIC PUMP 5 Sheets-Sheet 2 INVENTOR.

Dec. 26, 1967 D, C, HALSEY 3,359,913

HYDRAULIC PUMP Filed oct. 22, 1965 7 5 Sheets-Sheet 5 f 4 41NVENTOR- Dec. 26, 1967 D. c. HALSEY 3,359,913

HYDRAULIC PUMP Filed Oct. 22, 1965 5 Sheets-Sheet 4 Dec. 26, 1967 D, C HALSEY 3,359,913

HYDRAULIC PUMP Filed Oct. 22, 1965 5 Sheets- Sheet United States Patent O 3,359,913 HYDRAULIC PUMP David C. Halsey, Birmingham, Mich., assigner to Chrysler Corporation, Highland, Mich., a corporation of Delaware Filed Oct. 22, 1965, Ser. No. 501,450 10 Claims. (Cl. 10S-136) This invention relates to improvements in hydraulic pumps, particularly high pressure pumps suitable for use with automobile power steering mechanisms.

An important object of the present invention is to provide an improved balanced pump of the above character comprising a housing containing a cylindrical cam ring having an inner out-of-round cam surface. A cylindrical rotor mounted within the cam ring cooperates with the latters inner cam surface to provide a pair of diametrically spaced inlet chambers and another pair of diametrically spaced discharge or pumping chambers associated respectively with corresponding pairs of inlet and pumping arcs at the inner surface of the cam. The rotor carries a plurality of radially shiftable pumping elements such as slippers or rollers in fluid pumping and sealing engagement with the inner cylindrical surface of the cam, which latter also comprises a separate constant radius dwell or sealing arc spacing each pair of proximate ends of the pumping and inlet arcs.

The cam ring is conned between a pair of plates dened as a front plate and a pressure plate, between which the rotor is freely rotatable. A pair of radially spaced inlet ports communicate axially with each of the opposite sides of each inlet chamber to supply inlet iluid thereto, these inlet ports being provided in the front and pressure plates and being in turn connected with an inlet header extending coaxially around approximately two-thirds of the outer circumferential surface f the cam ring. Similarly, a pair of radially spaced discharge ports extending axially through the pressure plate communicate axially with each of the discharge chambers. A corresponding pair of high pressure balancing ports or recesses are provided in the front plate axially opposite each pair of discharge ports and in communication with the corresponding discharge or pumping chamber. The axially opposed inlet ports have equal areas exposed to the rollers and rotor to balance the axial fluid pressures thereon. For the same purpose the high pressure balancing recesses have areas equal to the areas of the axially opposed discharge ports.

The central portion of the inlet header communicates adjacent its mid-region with a radial supply port .in the housing to receive low pressure inlet fluid. The inlet iluid bifurcates as it enters the inlet header, flows circumferentially to the inlet ports at the opposite ends of the inlet header, then ilows axially into the inlet chambers. The low pressure inlet uid is carried by the rotor to the discharge chambers and discharged under high pressure through the discharge ports into a discharge header. A metering and bypass valve in communication with the discharge header conducts the high pressure fluid at a predetermined rate of flow to the power steering system and bypasses the remainder of the pump discharge fluid at comparatively high velocity to the supply port.

A portion of the pump housing at the region of the circumferentially extending inlet header is enclosed within a reservoir shell spaced from the exterior of the pump housing to provide a reservoir therebetween. A pair of fluid make-up ports in the portion of the housing which defines the outer wall of the inlet header open directly into the opposite ends of the latter from the reservoir at locations upstream of the inlet ports. Immediately upstream of each make-up port, the housing provides an integral projection into the inlet header to effect a venturi restriction and a consequent acceleration of the bypass iluid owing in the header in opposite directions from the supply port, so as to accelerate the flow of make-up uid through the make-up ports from the reservoir into the inlet header and inlet ports and to effect a particularly efficient supercharging and a complete filling of the inlet chambers with low pressure inlet fluid.

Other objects are to provide an improved compact arrangement in an automobile power steering pump and ow control valve for regulating the rate of flow of pressurized fluid from the pump to the power steering motor, which is particularly eicient in operation, simple in construction, economical to manufacture and assemble and has a compact simplied housing adapted to be readily fabricated by casting and broaching operations.

Another object is to provide a pump and ow control valve combination wherein, in cooperation with the radial supply port, the ow control valve comprises an annular spool shiftable axially in a bypass bore in the housing parallel and adjacent to the axis of the pump rotor. The discharge header of the pump is in communication radially with the -bypass bore at an upstream end of the valve spool, the bypass bore being also in communication with the supply port downstream of the valve spool.

Another object is to provide an improved hydraulic pump comprisingva cast steel housing body having a large intermediate chamber containing the cam ring and rotor and opening axially in opposite directions into coaxial bores. One of the coaxial bores is of reduced diameter and extends through a thickened load supporting portion of the housing body and carries a journal for a coaxial rotor shaft on which is keyed a power driven pulley. The other coaxial bore is sealed by an end closure or fixed outer plug which cooperates with the pressure plate to provide the discharge header therebetween, whereby the pressure plate is urged axially into abutment with the axial end surface of the cam ring by the uid pressure Within the discharge header.

In accordance with the foregoing, the discharge header is conveniently contained within the bore of one axial end of the housing body, the Huid pressure in the discharge header serving to maintain non-rotatable parts of the pump in axial abutment with a force proportional to the pump discharge pressure. In consequence, leakage between these parts is minimized when the pump is under load and operating at high pressure.

Another object is to provide such a pump wherein the pressure plate is provided with a socket closed at its outer end and opening coaxially inwardly toward the rotor and having a stub end of the rotor shaft, which extends axially through the rotor, journaled therein, thereby to provide convenient means for shielding the rotor shaft from exposure to the high pressure fluid and also for simplifying the sealing of the pump, particularly around the pulley end of the rotor shaft, to achieve a simplified economical pump structure having a hydraulically balanced rotor and shaft assembly. i

Other objects of this invention will appear in the following description and appended claims, reference being had to the accompanying drawings forming a part of this specification wherein like reference characters designate corresponding parts in the several views.

FIGURE l is a side elevational view with parts broken away showing a pump embodying the present invention;

FIGURE 2 is a right elevational View of the pump illustrated in FIGURE l, with portions broken away to show details of the pump mechanism;

FIGURE 3 is a longitudinal sectional. view through the rotor and bypass valve taken substantially in the direction of the arrows along the broken line 3-3 of FIGURE 2;

FIGURE 4 is a longitudinal sectional view through p the bypass and safety valves, taken substantially in the 3 direction of the arrows along the line 4 4 of FIG- URE 2;

FIGURE 5 is a longitudinal sectional view taken substantially in the direction of the arrows along the line 5 5 of FIGURE 2, showing details of the seal bleed ducts; f

FIGURE 6 is an elevational view of the cam side of the front plate, taken substantially in the direction of the arrows along the line 6-6 of FIGURE 3; and

FIGURE 7 is an elevational view of the cam side of the pressure plate taken substantially in the direction of the arrows along the line 7-7 of FIGURE 3.

It is to be understood that the invention is not limited in its application to the details of construction and arrangement of parts illustrated in the accompanying drawings, since the invention is capable of other embodiments and of being practiced or carried out in various ways.

Also it is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation.

Referring to the drawings a particular embodiment of the present invention is illustrated by way of example in a high pressure automobile power steering pump comprising a generally cup-shaped cast steel housing 10 open at its right end, FIGURE 3, to provide a circularly cylindrical pump chamber 11. The housing 10 provides an integral lower enlargement 10b containing an axially extending valve chamber 12 of circular cross-section also opening endwise in the same direction as the chamber 11. The left end of the housing 1t) comprises a thickened hu'b 10a and a bore 13 coaxial with chamber 11 and containing an annular bearing 14 for a rotor shaft 15. The present pump has several features common to the pump described in my co-pending application, Ser. No. 266,569, filed Mar. 20, 1963, now Patent No. 3,236,566, and reference thereto is hereby made for a possible better -understanding of such features.

'the rotor 20 rotates with shaft 15 and is freely slidable axially thereon. The circumference of the rotor 20 is provided with twelve axially extending and radially opening notches 22, each containing a cylindrical roller 23. The sides of the notches 22 diverge radially outwardly from a width measured circumferentially less than the diameter of the roller 23 to a width greater than the roller diameter, so as to enable each roller to move freely along the trailing edge of the corresponding notch 22 during operation of the pump as explained below.

The rollers 23 are restrained against radial movement by the out-of-round inner cylindrical cam surface 24 of a generally annular cam ring 25 having a cylindrical outer surface of circular cross-section coaxial with the rotor shaft and tting -closely and axially slidably within the chamber 11. The rotor and cam ring 25 space a front or base plate 26 from a pressure plate 27. The faces of the plates 26 and 27 which confront the cam ring are flush with the juxtaposed faces of the latter and extend perpendicularly to the axis of the rotor 15. In order to allow freedom of rotation of the rotor 20, its axial length in FIGURE 3 is slightly less than the axial length of the ring 25 by approximately .0008 for example. Similarly the axial length of the rollers 23 is approximately .0002 less than the axial length of the rotor 2t).

The outer cylindrical surfaces of the plates 26 and 27 fit closely and axially slidably within the chamber 11 and the outer face of plate 26 ts flush against the base 11a of the chamber 11. The plates 26 and 27 cooperate to confine the rotor 20 within `a pumping chamber bounded circumferentially by the cam surface 24 and are maintained in circumferential alignment with the ring 25 by means of an axially extending pin 28 which extends snugly through an opening in the ring 25 and is confined at its left end within the housing 10. Radially elongated holes 29 and 30 in the plates 26 and 27, FIGURES 6 and 7 respectively, accommodate thermal and production variations in the dimensions -of these parts.

The rear or endwise opening of the chamber 11 is closed by a plug 31 secured in position by a C-ring 32 partially embedded in the housing 10. Annular O-rings 33 and 34 around the plug 31 and pressure plate 27 respectively prevent axial leakage of high pressure fluid. The plate 27 is urged axially against ring 25 by a coil spring .35 seated within a pocket in plug 31, thereby to seat the plate 26 against the wall 11a and to seat the plates 26 and 27 against the axially opposite faces of the ring 25 in uid sealing relationship, which relationship is enhanced by the pressure of the pump discharge fluid contained within a fluid discharge header 36. The latter is confined between plate 27 and plug 31 and opens through a high pressure port 37 in the housing 10 into the right end of valve chamber 12. Extending rightwardly from the rotor 20 in FIGURE 3 is a shaft stub end 15a which projects into a cup-shaped pocket 38 in plate 27, the pocket 38 being closed at its right end and containing a bearing 39 for the stub 15a of shaft 15. An annular groove 40 in the shaft 15 adjacent the right edge of rotor 20 carries a C-ring 41 which serves as a thrust washer to prevent leftward separation of the shaft 15 from the pump assembly.

Referring to FIGURE 2, the cam surface 24 comprises a pair of diametrically opposed 30 sealing arcs 45 and 45a of constant diameter. Mutually spacing the sealing arcs 45 and 45a are another pair of diametrically opposed sealing arcs 46 and 46a of constant radius somewhat larger than the radius of the arcs 45 and 45a and extending circumferentially 35. Between each small constant radius sealing arc 45 or 45a and the next adjacent large constant radius sealing arc 46 or 46a, measured clockwise in FIGURE 2, is a 70"o intake arc 47 or 47a respectively of gradually increasing radius. Similarly, between each large diameter sealing arc 46 or 46a and the next clockwise adjacent small diameter sealing arc 45 or 45a is a 45 discharge arc portion 48 or 48a respectively of gradually decreasing radius. The curvature of cam surface 24 may =be determined in accordance with my aforesaid co-pending application.

At the sectors of the diametrically disposed intake arcs 47 and 47a, the housing enlargement 10a is provided with a pair of lobes extending axially outwardly from the front plate 26 and containing lluid inlet recesses or chambers 49 and 49a respectively, FIGURE 2. The radially outer portions of recesses 49 and 49a extend axially in the housing 10 at locations adjacent and radially outwardly of plate 26 and ring 25, as indicated at 5t) in FIGURE 3, to a circumferentially extending inlet header 51 coaxial with rotor 20 and located centrally within the housing 10 and partially overlapping the ring 25 and plate 27. Offset against the direction of rotation from the mid-portion of the header 51, the latter communicates with the valve chamber 12 to receive lluid therefrom through a radially outwardly converging supply port 52 in the housing 10, FIGURES 2 and 3. The supply port 52 is located adjacent the line of symmetry of the porting system but offset as aforesaid so as to supply inlet fluid adequately to both branches of the inlet header and to compensate for the direction of rotation of the rotor which tends to reduce the inlet pressure at the inlet ports 53a, 54a with respect to the inlet ports 53, 54.

Also located axially adjacent rotor 20 at the region of the chambers 49 and 49a respectively are a pair of outer inlet ports 53 and 53a in the plate 26. A similiar pair of outer inlet ports 53 and 53a are located in lplate 27 directly opposite the corresponding ports 53 and 53a. These outer inlet ports open axially toward the rotor and cam ring 25 and also open radially outward-ly into the charnber portion 50 and inlet header 51 to receive inlet fluid, FIGURE 3, and partially overlap the rollers 23 and the radially outer portions of the notches 22 to supply the latter with uid as they sweep across the inlet cam arcs 47 and 47a, FIGURE 2. R-adially inwardly of the ports 53 and 53a are a p-air of inner inlet ports 54 and 54a which extend axially through plate 26 to receive fluid from inlet recesses 49 and 49a and to discharge the fluid into the rotor notches 22 at locations radially inwardly of the rollers 23. Similar inner inlet ports 54 and 54a' are provided in the face of plate 27, which confronts rotor 20 directly opposite the ports 54 and 54a respectively. The transverse areas of the inlet ports of each axially opposed pair are identical, so as to maintain the rotor 20 and rollers 24 in hydraulic balance.

At the region of the discharge cam arcs 48 and 48a, the pressure plate 27 is provided with a pair of axially extending outer and inner arcuate discharge ports 55', 56' and 55a, 56a respectively, which merge to common discharge ports 57 and 57a in communication with discharge header 36, FIGURE 3. The radially outer discharge ports 55', 55al partially overlapthe rollers 23 and the outer portions of the notches 22, whereas the radially inner discharge ports 56', 56a open into the lower portions of the notches 22 radially inwardly of the rollers 23, to receive uid from the notches 22 upon inward movement of the rollers 23 during operation of the pump. Axially opposite the discharge ports 55', 55a', 56 and 56a' are pressure balancing notches 55, 55a, 56, and 56a respectively, formed in the surface of plate 26 confronting the rotor 2u to provide areas exactly equal `to the corresponding areas' of the axially opposed discharge ports in plate 27, so as to maintain the rotor 20 and rollers 23 in hydraulic balance. Y

Slidable axially within and completely filling the crosssectional area of valve chamber 12 is a hollow cylindrical slide valve 58 urged rightward against the pump discharge pressure by means of a coil spring 59 seated under compression between the left end of housing enlargement b and the right end of valve 58. The latter is provided with a metering orifice `60 opening into the right end of chamber 12 to receive the high pressure uid from port 37. Metered fluid entering port 60 ows axially through the tubular valve 58 and is discharged into passage 6'7 opening into the left endof chamber 12, FIGURE 3. The passage 67 extends through the housing enlargement 10b and integral boss 10c thereof and is connected by means of coupling 70 with tubular conduit 69 which` leads to the power steering gear 69a to actuate the latter, FIGURES 2 and 4.

The opening 60 is partially closed by a coaxial metering rod 61 extending into the valve 58 and terminating in an enlarged head 62 dimensioned to pass through the opening 60. The right end of rod 61 is threaded at 63 and adjustably screwed into a plug 64 which closes the right end of valve chamber 12 and is maintained in position against the tluid pressure within chamber 12 by means of a C-ring 66 partially embedded in the housing body 10b adjacent the exterior of plug 64. The latter is provided with a diametrically extending slot 65 adapted to receive a tool to prevent rotation of plug 64 upon angular adjustment of the .screw end 63.

The tension in spring 59 is predetermined with respect to the location of supply port 52 so that when the rate of fluid ow passing through metering port 60 equals a predetermined amount, as for example two gallons per minute required to operate the power steering gear 69a, pressure will build up on the right side of valve 58 and force the latter against the spring 59 to open communication between the right or high pressure end of chamber 12 and supply port 52 by reason of a reduced diameter portion 53a at the right end of valve 58. As valve 58 moves leftward to open port .52., with increasing pump speed,

6 metering port 60 will move leftward to receive the enlarged metering head 62 and thus reduce the rate of llow through port 60 to the steering gear 69a, as is desired during high speed operation of the vehicle engine which drives the pump.

Immediately upstream of the outer inlet ports 53 and 53a respectively, the housing 10 is provided with a pair of integral bosses 71 and 71a which extend radially outwardly from the portion of the housing 10 which contains the header 51, FIGURES l and 4. Inlet or fluid make-up ports 72 and 72a extend through the bosses 71 and 71a respectively transversely to the axis of rotor 20 and into header 51 from the exterior of the housing 10 at an angle inclined radially inwardly in the direction of circumferential flow in header 51. The exterior of housing 10 around ports 71, 71a comprises a reservoir 73 enclosed by an outer cup-shaped shell 74 or reservoir housing fitted over the rear or right end of the housing 10, FIGURE 3. Cast integrally with housing 10 so as to project angularly in the downstream direction into header 51 are a pair of venturi projections 68, 68a immediately upstream of the fluid make-up ports 72, 72a respectively.

The reservoir 73 is connected by a return port 74a with a return conduit 74b from the power steering gear 69a, FIGURE 2. Near its front end, the housing 10 has an integral annular seal retaining groove 7S eccentric with respect to rotor 20 and containing an annular O-ring seal 76. The latter is under compression between the juxtaposed portions of the housing 10 and shell 74 to prevent fluid leakage from the reservoir 73. Forwardly of the seal 76, the shell 74 terminates in an outturned reinforcing flange 77.

The pump is mounted on the engine by means of a bracket 78 pivotally secured to the engine and bolted to a pair of housing mounts 79 integral with the housing enlargement 10a forwardly of the reservoir shell 74. Portions 78a of the bracket 78 extend around the rear of the housing 10 and are bolted to plug 31 by means of bolts 81 which extend through the brackets 78a and reservoir shell 74 to clamp these members together. Leakage around the bolts 81 is prevented by an annular-seal 82. An upper annular flange 83 of the shell 74 denes an opening into the lower end of a cylindrical expansion chamber 84 which is welded to ilange 83. The upper end of chamber 84 is closed by a removable cap 85, whereby hydraulic fluid lost from the system by leakage may be readily replenished. Normally the fluid level will be maintained at approximately the level of line 84a.

Fluid which tends to leak radially from the discharge ports 55', 56', 55a', 56a and pressure balancing recesses 55, 56, 55a, 56a toward the shaft 15 is conducted from the right end of the latter by a bleed conduit 86 bored in the plate 27 from the inlet port 54 to the rear end of cylindrical chamber 38, FIGURE 3. Similarly, tluid leaking axially along shaft 15 to seal 17 is returned to the reservoir 73 by means of bleed conduit S7 bored in the housing hub 10a to a small central recess or pocket 88 cast within the thickened portion of housing 10a provided for recess 49a and the proximate mounting boss 79. The pocket 88 is located adjacent the outer periphery of the plate 26 at an upper location beyond the extent of the inlet ports and header 51. From the chamber 88, a second bore 89 extends in housing portion 10a into the reservoir 73, FIGURE 5. By virtue of this construction, drainage directly to the reservoir 73 from the interior of seal 17 is accomplished, so that operation of the pump does not tend to suck air axially inwardly through the seal 17, as for example, into one of the inlet ports. The inner end of the stub shaft 15a may be drained directly to the inlet port 54 as illustrated because this end is positively sealed from the atmosphere.

In order to etIect a smooth transition in the fluid pressure as the low pressure inlet fluid is carried along the sealing arcs 46, 46a to the high pressure discharge arcs 48, 48a, the leading edges of the inner discharge ports 56 and 7 56a are in communication with precompression recesses 90 and 90a respectively in the front plate 26. These recesses are generally triangular in their elevational views, FIGURE 6, and diverge in the direction of rotor rotation from their apices to their corresponding inlet ports. Similar decompression recesses 91 and 91a may be provided in the front plate 26 opening into the leading edges of `the inner inlet ports 54 and 54a respectively in order to gradually reduce the pressure of uid being transported through the sealing arcs 45 and 45a respectively to the inlet ports at the regions 47, 47a. Such notches may be provided alternatively in the plate 27 and are effective to reduce noise during operation.

In the event that the pressure to the steering gear 69a in duct 67 should exceed a predetermined limiting value, a suitable relief valve is provided which discharges to the reservoir 73. In the present instance, a bore 92 in the housing enlargement 10b opens at one end into the duct 67, FIGURE 4, and at its other end enlarges at 93. A tube 94 sealed within the bore 92 communicates with the duct 67 and extends coaxially into the bore enlargement 93. The outer end of the tube 94 provides a valve seat for a spherical check valve 95 normally held in position to close tube 94 by a cup-shaped retainer 96 slidably sleeved closely over the outer end of tube 94 and provided with pressure discharge ports 97 adjacent the ball 95. A coil spring 98 coaxially around retainer 96 is under compression between an inner annular ange 96a of the latter and an outer end closure plug 99 which closes the outer end of the bore enlargement 93. Thus the ball 95 is maintained in its closed seated position by the force of spring 98 until the pressure within duct 67 exceeds the aforesaid predetermined limiting value. Above this value the ball 95 is unseated against the pressure of the spring 98, whereby the iluid pressure within duct 67 is discharged via ports 97 into the bore enlargement 93 and thence via port 166 into reservoir 73. The port 100 extends radially with respect to the axis of tube 94 and sleeve 96 and is preferably located adjacent the ange 96a axially remote from the ports 97.

In operation of the structure described, upon clockwise rotation of the rotor in FIGURE 2, as the rollers 23 ride along the surfaces of cam 24 at the inlet sectors 47 and 47a of increasing radius, fluid is forced into the gradually expanding volume of the notches 22 unoccupied by the rollers 23 and is carried across the sealing arcs 46 and 46a of large constant cam radius and discharged under pressure into the ports 55', 56', and 55a', 56a as the rollers are forced radially inwardly into the notches 22 by the decreasing cam radius at the arcs 48, 48a. The inlet sectors 47, 47a are separated from the adjacent discharge sectors 48, 48a by at least one roller 23 within each of the sealing arcs 45, 45a, 46, 46a. In this regard, a seal is effected at the sealing arcs between the roller Z3 thereat and both the trailing edge -of the notch 22 and the portion of the cam surface 24 in contact with the roller 23. By virtue of the extent of the sealing arcs 45, 45a and 46, 46a, spacing the inlet ports and discharge ports, the circumferential extent of the inlet and discharge ports can be readily dimensioned to facilitate lling of the notches 22 at the intake portion of the cam arc.

This latter function is aided by the bifurcation of inlet header 51 from the centrally located bypass Ior supply port 52, located adjacent the line of symmetry of the inlet porting system, to the diametrically opposed inlet ports at the arcs 47, 47a. Thus at the regions of the venturi projections 63, 63a, the inlet flow in header 51 is accelerated by venturi action to effect a supercharging of the makeup fluid, entering via ports 72, 72a, into each of the axially directed inlet ports 53, 53a and 53', 53a', as well as into the inlet ports 54, 54a. The bifurcated inlet header 51 in cooperation with the wrap around reservoir 73 enable the provision of short low resistance make-up ports 72, 72a directly into the header 51 from the reservoir 73. By virtue of the foregoing, cavitation and noise during the inlet operation of the pump are substantially avoided.

The high pressure Huid discharged through ports 57, 57a to the header 36 reacts against and holds the pressure plate 27 in sealing engagement with the cam ring 25, the latter in turn being urged in sealing engagement against the front plate 26 which is thus urged in sealing engagement against the base wall 11u, all with a force which is proportional to the pump discharge pressure. Accordingly leakage from the high pressure pumping arc regions 48, 48a radially toward shaft 15 and Icircumferentially toward the low pressure inlet arcs 47, 47a is substantially eliminated. Fluid that does leak through the high resistance leakage paths provided, as for example to the inside of seal 17, will be at low pressure and is returned to reservoir 73 or the fluid inlet system as explained above.

The discharge pressure from header 36 is conducted to the right end of slide valve 58 and through the metering orice 60 to the power steering gear 69u, thence back to the reservoir 73 via return line 74b and port 74a. The excess fluid discharged from the pump during high speed operation opens valve 58 against the force of spring 59 and is thus bypassed into supply port 52. Simultaneously the leftward movement of valve 58 causes the enlarged metering head 62 to enter and restrict metering orice 69 so as to reduce the rate of ow to the power steering gear 68 during the high speed operation of the engine driven pump when the .steering reaction force is a minimum.

I claim:

1. In a fluid pump, a housing, cam means in said housing defining a pump cavity, said housing having a pair of coaxial openings spaced by and communicating with said cavity, inlet and outlet ports communicating with said cavity to supply iluid thereto and to discharge fluid therefrom respectively, a rotor shaft having oppositely directed end portions extending coaxially into said openings respectively, pumping means carried by said rotor shaft in said cavity for pumping said fluid from said inlet port to said discharge port, means providing a bearing support for one of said rotor end portions within one of said openings, a pressure plate slidable axially within the other of said openings, an outer closure -member for said other opening and secured therein axially endwise of said pressure plate and cooperating therewith to define a discharge header therebetween, means connecting the fluid pressure at said discharge port with said discharge header to urge said axially slidable pressure plate toward said pumping means and against said cam means with a force proportional to the discharge pressure of said pump, and means supporting the other of .said rotor end portions and sealing the latter from the pressure in said discharge header comprising a central cup-shaped portion of said pressure plate providing a recess opening toward said cavity and having said other rotor end portion journaled therein, the last named means also comprising confronting annular sealing portions of said pressure plate and pumping means around said recess and mating to effect a high resistance uid leakage path therebetween into said recess.

2. In the c-ombination according to claim 1, means connecting said recess provided by said cup-shaped portion with said inlet port including fluid return duct means in said pressure plate extending from said recess to the side of said pressure plate confronting said pump cavity at a locationradially outwardly of said annular sealing portion of said pressure plate.

3. In the combinataion according to claim 1, said inlet and outlet ports being formed in said pressure plate at circumferentially spaced locations adjacent the o-uter periphery of said pumping means and communicating axially with said pump cavity, and a uid return duct extending in said pressure plate radially outwardly from said recess provided by said cup shaped portion to a region of said pressure plate in communication with said inlet port.

4. In a fluid pump, a housing, a cam ring in said housing defining a pump cavity, said housing having a pair of coaxial openings spaced by and communicating with said cavity, a rotor rotatable within said cavity, a rotor shaft secured coaxially to said rotor and extending in one axial direction from said rotor into one of said openings and journaled therein, said cam ring extending around said rotor and cooperating therewith to provide circumferentially spaced pumping and inlet chambers, portions of said housing being spaced from said cam ring to provide an inlet header extending circumferentially of said cam ring between the outer circumference of the latter and said housing, an inlet port connecting said inlet header with said inlet chamber, a discharge port opening into said pumping chamber to receive pressurized fluid therefrom, a plurality of pumping members carried by said rotor and engaging said cam ring to effect fluid seals between said discharge and inlet ports and also to pump fluid from said inlet port to said discharge port in the direction of rotation of said rotor, a discharge header in the other of said openings, said discharge port opening into said discharge header to discharge pressurized fluid thereinto, said housing having a drain recess therein at a location adjacent the outer periphery of said cam ring and spaced circumferentially between proximate inlet and discharge ports, said housing having portions separating said drain recess from both of the latter ports and blocking communication therebetween, a drain duct in said housing connecting said one opening with said drain recess, a fluid reservoir in communication with said inlet header, and a second drain duct in said housing connecting said drain recess with said reservoir.

5. In the combination according to claim 4, a front plate spacing said rotor from portions of said housing around said one opening and cooperating with said housing to define said drain recess and seal the latter from said proximate inlet and discharge ports, said front plate having an opening coaxial with said one opening for passage of said rotor shaft therethrough, a fluid container mounted on said housing and spaced therefrom, said container enclosing the portion of said housing having said other opening and cooperating with said housing to define said reservoir in the space between said housing and container.

6. In a fluid pump, a housing, a cam ring in said housing defining a pump cavity, said housing having a pair of coaxial openings spaced by and communicating with said cavity, inlet and outlet ports communicating with said cavity to supply fluid thereto and to discharge fluid therefrom respectively, a rotor shaft having oppositely directed end portions extending coaxially into said openings respectively, pumping means carried by said rotor shaft in said cavity for pumping said fluid from said inlet port to said discharge port, means providing a bearing support for one of said rotor end portions within one of said opening, a front plate spacing said pumping means and cam ring from a portion of said housing around said one opening, said front plate having its outer periphery in sealing contact with said housing adjacent the periphery of said cam ring and having a central opening coaxial with said one opening for passage of said rotor shaft therethrough, a drain recess in said housing at a location adjacent the outer periphery of said cam ring and spaced circumferentially between said inlet and an outlet port, said housing and front plate defining said drain recess and blocking communication lbetween the latter and both of said ports spaced thereby, a pressure plate slidable axially within the other of said openings and abutting said cam ring, said pressure plate having an annular bearing portion providing a bearing support for the other of said rotor end portions, an annular outer closure member for said other opening secured therein axially endwise of said pressure plate and cooperating therewith to define an annular discharge header therebetween, means connecting the fluid pressure at said discharge port with said discharge header to urge said axially slidable pressure plate against said cam ring with a force proportional to the discharge pressure of said pump, a container mounted on said housing and spaced therefrom, said container enclosing the portion of said housing having said other opening and cooperating with said housing to define a reservoir in the space between said housing and container, a drain duct in said housing connecting said one opening with said drain recess, and a second drain duct in said housing connecting said drain recess with said reservoir to drain fluid leaking axially endwise along said one rotor end portion.

7. In the combination according to claim 6, both of said drain ducts extending in said housing radially outwardly from the axis of said rotor shaft and obliquely thereto in the direction Ifrom said one opening to said other opening.

8. In a fluid pump, a housing, a rotor rotatable within said housing, a cam element extending around said rotor and cooperating therewith to provide two pumping chambers and tWo inlet chambers mutually spacing each other circumferentially, an inlet header extending circumferentially around said element between the latter and said housing, a pair of circumferentially spaced inlet ports connecting said inlet header with said inlet chambers respectively, a pair of circumferentially spaced discharge ports connected with said pumping chambers respectively to receive pressurized fluid therefrom, means carried by said rotor and cooperable with said cam element and the pumping and inlet chambers thereof to pump fluid from each inlet port to the next successive discharge |port in the direction of rotation of said rotor, a fluid supply port opening into said inlet header at a location between said inlet ports to supply pressurized fluid thereto, a container enclosing an exterior portion of said housing overlying said inlet header adjacent and upstream of said inlet ports and spaced from said housing to define a reservoir between said container and housing, a pair of fluid make-up ports extending directly through said housing from said reservoir into said inlet header at locations immediately upstream of said two inlet ports respectively, and means for utilizing the velocity of fluid flow in said inlet header to effect a supercharging of make-up fluid from said reservoir into said pair of inlet ports comprising a pair of venturi restrictions in said inlet header immediately upstream of the openings respectively of said two make-up ports into said inlet header, each restriction being defined by an integra-l boss of said housing extending into said inlet header.

9. In the combination according to claim 8, each makeup port extending from said reservoir into said inlet header an gularly thereto in the direction of fluid flow therein, the downstream edge portion of the boss defining the associated venturi restriction also defining the upstream edge of the opening of said make-up port into said inlet header, and means for supplying pressurized fluid to said fluid supply port.

10. In the combination according to claim 8, Said discharge ports opening axially into said pumping chambers at locations radially inwardly of said inlet header.

References Cited UNITED STATES PATENTS 2,924,182 2/1960 Blasutta et al. 103-136 3,076,414 2/1963 Adams 103-136 3,187,678 6/1965 Pettibone 103--136 3,194,168 7/1965' RoSaen 103--126 3,204,565 9/ 1965 Kirkpatrick 103-136 3,204,566 9/1965 Feroy 1013-216 3,207,077 9/1965 Zeigler et al. 103-136 3,236,566 2/1966 Halsey 103--136 3,257,958 6/1966 Adams et al. 103-'l36 DONLEY J. STOCKING, Primary Examiner.

WILBUR I. GOODLIN, Examiner. 

1. IN A FLUID PUMP, A HOUSING, CAM MEANS IN SAID HOUSING DEFINING A PUMP CAVITY, SAID HOUSING A PAIR OF COAXIAL OPENINGS SPACED BY AND COMMUNICATING WITH SAID CAVITY, INLET AND OUTLETS PORTS COMMUNICATING WITH SAID CAVITY TO SUPPLY FLUID THERETO AND TO DISCHARGE FLUID THEREFROM RESPECTIVELY, A ROTOR SHAFT HAVING OPPOSITELY DIRECTED END PORTIONS EXTENDING COAXIALLY INTO SAID OPENINGS RESPECTIVELY, PUMPING MEANS CARRIED BY SAID ROTOR SHAFT IN SAID CAVITY FOR PUMPING SAID FLUID FROM SAID INLET PORT TO SAID DISCHARGE PORT, MEANS PROVIDING A BEARING SUPPORT FOR ONE OF SAID ROTOR END PORTIONS WITHIN ONE OF SAID OPENINGS, A PRESSURE PLATE SLIDABLE AXIALLY WITHIN THE OTHER OF SAID OPENINGS, AN OUTER CLOSURE MEMBER FOR SAID OTHER OPENING AND COOPERATING THEREWITH TO DEFINE A DISCHARGE SURE PLATE AND COOPERATING THEREWITH TO DEFINE A DISCHARGE HEADER THEREBETWEEN, MEANS CONNECTING THE FLUID PRESSURE AT SAID DISCHARGE PORT WITH SAID DISCHARGE HEADER TO URGE SAID AXIALLY SLIDABLE PRESSURE PLATE TOWARD SAID PUMPING MEANS AND AGAINST SAID CAM MEANS WITH A FORCE PROPORTIONAL TO THE DISCHARGE PRESSURE OF SAID PUMP, AND MEANS SUPPORTING THE OTHER OF SAID ROTOR END PORTIONS AND SEALING THE LATTER FROM THE PRESSURE IN SAID DISCHARGE HEADER COMPRISING A CENTRAL CUP-SHAPED PORTION OF SAID PRESSURE PLATE PROVIDING A RECESS OPENING TOWARD SAID CAVITY AND HAVING SAID OTHER ROTOR END PORTION JOURNALED THEREIN, THE LAST NAMED MEANS ALSO COMPRISING CONFRONTING ANNULAR SEALING PORTIONS OF SAID PRESSURE PLATE AND PUMPING MEANS AROUND SAID RECESS AND MATING TO EFFECT A HIGH RESISTANCE FLUID LEAKAGE PATH THEREBETWEEN INTO SAID RECESS. 